Facial Expression Categorization by Chimpanzees Using Standardized Stimuli - Essay Example

Four experiments were conducted onchimpanzees using a set of standardized, prototypical stimuli created using the newChimpFACS coding system. 1) The first experiment was to determine whether chimpanzees could discriminate the3D facial expression figures in a MOT (matching-to-sample). It was a reproduction ofthe study by study by Parr, Hopkins, et al. (1998) Procedure: Data were collected on experimenting 6 male and female chimpanzees aged11 years and above. They were tested in their home cage.

The computer placed in anaudio visual cart was positioned about 30 cms from the cage and the eye of each animalwas about 40 cms from the computer. A joystick was attached protruding 4 cms into themesh. The experiments conducted were: 1) Initial Discrimination of Poser Stimuli 2)Inversion Effect for Facial expression 3) Examining Perceived Dissimilarity usingMultidimensional Scaling 4) Discriminating Facial Expressions using ComponentMovement. Experiment 1:The aim of this initial experiment was to verify whetherthe Poser facial expression stimuli were prominent for the subjects, and whether it couldbe discriminated at high levels of skill and that expressions were dealt with no evidentparent stimulus biases.

The analysis showed that 'scream' was the most salientexpression to single out. In fact the subjects reached the final testing criteria for screamsin minimum time.Experiment 2:Experiment 2 revealed a significant inversion effect suggesting a generalconfigural processing strategy for all expressions.Experiment 3:Subjects' pattern of error when differentiating all expressions. Apart from screams and pant-hoots showed much difference based on the identity of thefoil expression. They share the majority of their individual component movements, suchas the bared-teeth display, the presence of these similarities did little to confuseperformance.

The MDS analysis provides a statistical interpretation of howexpressions were categorized based on their perceived dissimilarity.Experiment 4:The results showed that for each facial expression, at least one component movement wasseen to